1. Field of the Invention
The invention relates to a method and system for recovering a catalyst for a fuel cell.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-A-2004-171921 describes a technology for recovering a catalyst or a carrier on which the catalyst is supported. According to the described technology, a membrane-electrode assembly (MEA) of a fuel cell is dissolved and insoluble elements are separated from a solution by a centrifugal separator or a filter, whereby the catalyst or the carrier on which the catalyst is supported, contained in the insoluble elements, are recovered.
According to the described technology, the catalyst (Pt) is barely separated from ink of the catalyst before the MEA is formed. However, there has not been established a method for efficiently separating the catalyst (Pt) or the carrier on which the catalyst is supported (carbon on which Pt is supported) from other elements (an electrolyte and diffusion layers) after electrodes are formed. For example, it is difficult to recover the catalyst or the carrier on which the catalyst is supported from an already-assembled fuel cell (e.g. a fuel cell that turns out to be defective after the electrodes are formed, a fuel cell of which the evaluation has been finished and which is no longer necessary, and a fuel cell that has reached its end of life). Also, separating the catalyst or the carrier on which the catalyst is supported somehow from the other elements increases the cost. For these reasons, it is almost impossible to recover the catalyst or the carrier on which the catalyst is supported. Accordingly, the reliability for recovery of the catalyst or the carrier on which the catalyst is supported remains low. For example, because the carbon on which Pt is supported and the carbon that forms the diffusion layers have substantially the same mass and size, it is difficult to separate these carbons from each other using a centrifugal separator or a filter.